1. Field of the Invention
Aspects of the present invention relate to a shift register circuit, and more particularly, to a shift register circuit provided in an organic electroluminescent display and sequentially outputting signals different in polarity.
2. Description of the Related Art
In general, an active matrix display such as an organic electroluminescent display is provided with a pixel array matrix in a region where data lines and scan lines intersect with each other.
Here, the scan lines form horizontal lines (row lines) of a matrix pixel portion, through which predetermined signals are sequentially supplied by a shift register circuit provided in a scan driver.
Such a shift register is widely classified into a dynamic shift register and a static shift register. The dynamic shift register needs a relatively small number of thin film transistors (TFT) per stage and has a simple structure, but the dynamic shift register has shortcomings that a frequency band for a clock is narrow and power consumption is relatively high.
On the other hand, the static shift register needs a relatively large number of TFTs per stage, but it has advantages that the frequency band for the clock is wide and power consumption is relatively low.
For a shift register to be mounted in the active matrix display such as the organic electroluminescent display, it is important to decrease the number of TFTs as long as functions of the shift register are not deteriorated. However, it is more important to secure high reliability and low power consumption in the circuit operation.
Further, as the organic light emitting display has recently become larger having a large-sized panel, the scan driver to be mounted in the panel should include the shift register, thereby reducing the size, the weight and the production cost of the organic light emitting display. However, the conventional shift register includes a p-type metal oxide semiconductor (PMOS) transistor and an n-type metal oxide semiconductor (NMOS) transistor, so that it is difficult to mount it on the panel. Further, the conventional shift register including the PMOS transistor and the NMOS transistor consumes much power because a predetermined static current flows through the transistor while generating an output signal.